DENVER (AP) — More than 2,000 flights have been canceled over the weekend at Denver International Airport as a major snowstorm strikes the region.

The National Weather Service has issued a winter storm warning, saying it expects 18 to 24 inches (46-61 cm) of heavy, wet snow to fall in Denver and Boulder from Saturday afternoon through Sunday night. Some areas along the Front Range foothills were expected to receive up to 30 inches (76 cm).

The Colorado Department of Transportation warned that road closures are highly likely and asked people not to make unnecessary trips. The highways most likely to be affected included Interstate 25 from Colorado Springs to Wyoming, including Denver and Monument Hill; I-70 to Limon; and I-76 to Ft. Morgan, the department said.

Denver International had a busy morning Saturday with passengers trying to beat the storm, but about 750 flights later in the day were canceled, airport spokeswoman Emily Williams said. Just about all Sunday flights had been canceled as well — nearly 1,300.